Methods and compositions for spraying metal



Patented Mar. 7, 1939 r OFFICE METHODS AND COMPOSITIONS FOR SPRAYING IVIETAL Frank Osborn Albertson and Gustav A. Olsen,

Sioux City, Eowa,

assignors to 'Albertson &

Company, Inc., Sioux City, Iowa, a corporation of Iowa No Drawing.

Application February 23, 1937-,

' Serial No. 127,179

2 Claims.

application, Serial Number 80,372, filed May 18, I

The present methods and compositions may be used wherever it is desirable to secure a coating .10 or a filling of metal upon an aluminum metal surface, and we do not wish to be limited to the specific examples which at present constitute the widest application of the invention.

By way of example, however, the invention is 15 being applied to the repair of automobile bodies,

fenders, etc., for filling depressions or dents with metal, which may be dressed down flush with the other surfaces of the automotive vehicle body parts to present a contour which. is the same as 20 that of the body before the damage to the body.

The present method is of particular advantage in this connection because the body parts are not heated and there is no warping due to the heat of the body parts nor any melting norburnnig 25 of the sound insulating asphalt or tar coverings which are used on the inside of the modern steel automobile bodies.

One of the most important objects of the present invention is the provision ofan improved v 30 method of metal coating or filling and improvedcompositions for such methods by means of which the coating or filling is so intimately bonded or secured to the work piece that there is no possibility of separation due to the vibration or stress 35 and strain to which automotive body parts" are subjected in use. This object is so important that it may be regarded as absolutely essential to l the success of any such method or composition because a filling or coating which will not stick 40 to the automotive body part is absolutely useless and a waste of time iriso far as the user of the process is concerned. v

Another object is the provision of an improved cold tinning compound which is adaptable to use 45 in tinning aluminum after the aluminum has been treated with an additional supplementary wash, to render the aluminum susceptible to tinning with the present compound.

Another object is the provision of a supple- '50 mentary composition in the form of an aluminum wash which may be applied to an aluminum work piece in order to prepare it for the ti'n'ning of the piece by a standard cold tinning compound of the type described herein.

55 Another object is the provision of animproved cold metal spraying process by means of which a metal filling may be so firmly and intimately bonded to a metal work piece that the filling or coating is, for all practical purposes, an integral part of the work piece and it is not necessary to resort to mechanical bonding devices, such as roughening the surface, or the like.

Other objects and advantages will be apparent from the following description, in which various examples of the application of the process and 10 the compounding of the composition are given.

The present methods may be carried out by hand, with the use of various implements of the most'simple type, to which reference will be made" during the description of the process. They are, however, most expeditiously carried out by the use of improved tools, such as sanding machines, metal spray guns, and paint spraying devices, to which reference will also be made.

For example, the complete method of preparing an automotive vehicle fender or body part may be carried out as follows: Assuming that the body of an automotive vehicle has a. dent in it, which it is desirable to fill with sprayed metal, the surface of the body surrounding the-dent must first be thoroughly cleaned. This may be done by hand by means of scraping devices, sand paper, steel brushes, etc., but the operation is most quickly performed by the use of a disc sander.

Such a sander is disclosed in the prior patent of Frans O. Albertson No. 1,954,977, issued April 17, 1934, when equipped with the abrasive disc of U. S. Patent .No. 1,882,693 to Frans O. Albertson, et al., issued October 18, 1932.

In order to enable the operator to secure a feather edge on the filling, the surface of the work piece should be sanded clean over an area extending about one inch around the proposed metal fill. All hammering and bumping out of the area of the work piece should be done before 0 applyingthe metal. No acid nor paint removed should be applied to the metal work piece.

After theisurface has been cleaned satisfactorily, it should be tinned with a cold tinning compound adapted to prepare the surface for the application of the metal. A satisfactory tinning compound is very important to the success of the process, and so far as we are aware none of the tinning compounds of the prior art are capable of producing satisfactory results.

A suitable cold tinning compound for steel,

I which may also be used for aluminum, whenthe for steel or other ferrous be renewed from time to time may be embodied loses the effectiveness of some of its properties in so far as its application to steel is concerned, when it has been fore, the compound is preferably made powder form and is sold to the user together with a reviver comprising a solution which is to be mixed with the powder compound or base immediately prior to its application, when the compound is to be-used for tinning ferrous metals.

When the compound is to be used for tinning aluminum, the powder should be mixed with the reviver, and should stand covered for at least twelve hours to season, and only the seasoned tinning compound should be used on aluminum, after the aluminum'w'ash has been applied.

A suitable dry tinning compound base in the form of powder may be made up as follows:

Base in form of powder Percentage by weight Metallic mercury (by weight) (28 ounces)--- 42 Crystolon (abrasive) (3% ounces) 6 Quartz sand (22% ounces)"; 34 Bichloride of mercury (12 ounces) 18 In some foreign countries the laws prohibit the use ofbichloride of mercury in commercial products. In such case,-the bichloride of mer-' cury is replaced by 12 ounces (by weight) of borax powder. The borax powder base also works in the cold tinning of metals, but is not as effective as the base which includes bichloride of mercury. I

The elements of the cold tinning compound metals which need to in a solution which we prefer to call the .Reviver. The reviverfmay consist of the following elements, in theproportions stated:

One pound, 14 ounces dissolved in water to make-2920 centimeters of cupric sulphate solution.

Reviver I Percentage by volume Cupr'ic sulphate solution Zinc chloride U. S. P. solution (350 cc. Hydrochloric acid,- 1.18 specific gravity 7 (350 'cc.) 10

The'base powder and the reviver are mixed' together by means of a wooden paddle and areviver solution mixed with 4 ounces of the. base powderwill make one small jar of the.

cold tinning compound suitable for-steel and g for aluminum, provided the aluminum has been previously treated as described herein.

In the case ofan application of sprayed metal to aluminum, it is important that the mercury of the compound does not come in contact'with anyaluminum. Metallic mercury tends to combine chemically with aluminum'and :causes it to bloom; that is, the metallic mercury attacks the aluminum and forms a chemical compound on the surface of the aluminum, which builds up rapidly. Therefore, it is evident that any tinning compound which includes metallic mercury cannot be successfully used if the metallic mercury the aluminum, as it would if the cold tinning mixed for a long time. Thereup in r from the unprotected of cupric sulphate is pound on steel. The .Wash is as follows:

(2920 cc.) so

comes in direct contact with 12 ounces of water to make 1250 This silver nitrate solution. is mixed with nitric 'acid in the following proportions:

Y Percentage by weight Silver nitrate solution (1250 cc.) 99.2 Nitric acid (1.28 specific gravity) (10 cc.) .8

Silver nitrate crystals by weight in the solution equal about 25%. These elements are thoroughly mixed to'geth'e, and whenever an aluminum surface is to be. tinned it is first cleaned with a sanding disc and then protected from the. cold tinning compound by means of the aluminum wash. A suiiicient area outside,

tinned should be covered, to protect the aluminum from the cold of the sanded surface to be tinning compound, which is injurious to the bare aluminum surface. A brush is furnished with a bottle of the aluminum wash", and it may be applied in the same manner as paint is applied. The mercury present in the cold tinning compound is injurious to aluminum, and it is very important that the compound be kept away aluminum surface. Furthermore, we recommend .that any materials such as compound paddle, rags, and even a container, or any water that has been used with aluminum wash, and kept away from the base compound, as the smallest particle of aluminum wash mixed withthe base. compound will be detrimental to the application of the base tinning com,- action of the aluminum Aluminum may be plated with silver, and the silver nitrate applied to the cleaned aluminum Surface acts to combine with the aluminum to form a layer of silver on the aluminum. The silver layer positively protects the aluminum from the direct action of metallic mercury. The

nitric acid tends to clean the aluminum surface for the application of the, silver. The cold tin-.

ning compound for steel may then also be used for aluminum after the aluminum has been protected withthe aluminum wash.

In order that the operation of the cold tinning compound on the metal work piece may be understood, we shall describe in greater detail one theory of its operation. The cold tinning compound for steel includes the quartz and Crystolon abrasive for the purpose of aiding in the cleaning of the work surface through the abrasive action of these materials, and. in order to give the compound a suitable body. The Crystolon abrasive is primarily for the purpose of abrasion, while the quartz is primarily for the purpose of giving body to the compound.

A silver layer on the aluminum canbe plated with copper by the application of a copper sulphate ,solution to the properly cleaned surface. This is the purpose'oi the use of copper sulphate in the reviver. The hydrochloric acid and zinc chloride are believed to act as a flux or cleanser in removing the oxide film from the metal, as-

be used only on aluminum sisted by the abrasive, which exposes new metal surface to the action of the composition.

The bichloride of mercury goes into solution, and is adapted to combine with the copper, which becomes applied to the steel surface to form an amalgam of mercury, which is further adapted to combine with thefree metallic mercury in the compound, to provide a more substantial coating of mercury over the copper plating. The silver adheres to the aluminum and the copper to the silver, and the mercury combines with and adheres to the copper, forming a tinned surface which also includes zinc 'of the zinc chloride solution. This. tinned surface'ltias the appearance of bright tin, and is adapted to effect an intimate and secure bond between the sprayed metal and the aluminum work piece.

After the aluminum has been suitably coated with the silver wash solution, the cold tinning compound for steel may be applied to aluminum as follows: A wooden paddle is provided for mixing the compound thoroughly, and for applying it to the metal surface. The compound is ap: plied to all parts of the surface with the wooden paddle; A thick felt pad orapplicator with a metal handle is provided for the purpose of rubbing the compound into the surface of the metal. The felt base applicator should be thoroughly soaked with distilled water so that the liquid ingredients of the compound will not be lost by soaking into the felt. The applicator may then be wet with the reviver, which is first applied and afterward used to apply the base of the compound, and the surface should be thoroughly rubbed until it presents the appearance of a brightly tinned surface. The excesscompound should then be wiped off with a clean] dry cloth, which also brings out the bright finish. If the surface is not uniformly tinned, as indicated by its uniform bright appearance, more compound should beapplied with the wooden paddle and rubbed in with the felt applicator.

Under no circumstances should'the dry tinning compound be applied to aluminum before using a silver wash.

After the metal has a suitably tinned surface, the step of spraying the metal comes next in the application of providing a metal coating or filler. This step is preferably carried out by means of a metal spray gun of the prior patent of Frans O. Albertson, No. 2,058,653, issued October 1936, but the spraying may also be carried on by hand, with the use of the following implements:

The metal to be sprayed is melted in a metal well formed in a metallic body which is adapted to withstand the temperatures at which the sprayed metal melts. This metallic body preferably has a tapered bore which forms the metal well and. which terminates in a metal nozzle.

In the case of a hand implement it might be embodied in a ladle with a supply of melted spray metal-and terminating'in a suitable nozzle.

Air is supplied by means of an air nozzle, pref erably of the shape shown in said prior patent of Frans O. Albertson, having a nozzle opening in the form of a curved slit, which may embrace the end of the metal nozzle, when the air nozzle is properly positioned with respect to the metal nozzle. The spraying is brought about by the action of the air on the metal emerging from the metal nozzle of the metal well, and the two nozzles should preferably be held quite close to the work, at a distance of from one to two inches from the work piece.

When the metal spray gun of said prior patent on steel or other ferrous metals.

is used, it is necessary to latch the trigger in closed circuit position and to permit the gun to heat up for about five minutes. When a metal stick touched to the nose end of the gun melts, then the gun is hot enough to work. Further pressure on the trigger causes the air valve to be opened, and permits air to issue from the air nozzle.

The metal to bev sprayed upon the prepared tinned surface maybe any standard solder metal, preferably in the form of sticks, so that the stick can be fed into the metal well of the gun, as desired. The amount of metal is controlled by the hand feeding of the stick, more metal being melted and supplied when a greater pressure is applied to the stick.

It is important that the metal alloy be pure and clean inorder to make sure that it will adhere firmly to the prepared surface.

With a gun of the type described in said patent, air pressure at from 55 to 90 pounds is used, the gun requiring about seven cubic feet per minute at '70 pounds. The air should be dry, and the water' should be drained from the air line. The metal well in the gun should be carefully cleaned before and after spraying, and a blow out tool that is provided with the gun should be used to deflect the air up into the well to clean out the metal nozzle.

A fine, evenly distributed spray of metal should be sprayed upon the prepared surface, and the operator should first spray a thin layer of metal,

covering the entire tinned surface. The nozzle should be moved in a circular motion around the outer edge, and toward the center, with a uniform control of the air and uniform feeding of the metal.

Should a blotch of molten metal be blown upon the job, it should be removed and the spray evenly applied. When more. than one place is to be repaired, each place should be tinned and sprayed, one at a time. Any spray dust appearing' upon a sanded surface, after tinning one place, should be removed before that place is tinned, preparatory to its being sprayed. The spray should be continued and applied uniformly until the metal is built up and until all indentathe work piece so that it may be sanded down to the desired finish and level in order to provide a smooth surface for the application of the paint.'

The sprayed metal filling should then be sanded down, preferably with a disc sander of the type referred to above, and the sanding should be continued until the edges of the filling are'dressed down to a smooth feather edge and until all parts of the filling are flush with the surface of the work piece, or shaped as desired.

In case it is found, ,after sanding the sprayed metal, that the surface has not been built up sufficiently above the desired finishing level, so that it is necessary to spray more metal on the filling, then'the surface should be sanded smooth preliminary to the second application of the tinning compound.

The tinning compound for steel as described above purposely includes an excess of metallic mercury over that required for effective tinning one-fourth as much metallic mercury, or seven ounces of metallic mercury, would be sufilcient for the purpose of tinning steel surfaces in the compound, but we have discovered that the same Approximately be resprayed by using an excess of metallic mercury as described.

The smooth filler surface is then tinned with the same compound, which is applied in the same manner, with a wooden paddle, and rubbed in be continued until all the black spots have disappeared. The surface should then be sprayed at once, before the mercury in the compound hardens.

In the case of a respraying operation, however, it is important that the respraying be done immediately after the double application of the tinning compound, as the mercury seems to be absorbed from the surface by the filler metal and the tinned surface is effective only if sprayed immediately.

It will thus be observed that the same cold tin-' ning compound which is used for steel according to the present invention may also be used for tinning a sprayed metal surface for a respraying ed with aluminum wash,

operation. This was not possible with any of the compounds of the prior art, and so far as we are aware has never been accomplished before by theuse of any compound.

Before painting a surface which has been treatthe surface should be washed, including the feather edges and every part to which wash or compound has been applied, with a caustic soda solution, to effect a thorough cleaning. v

If for some reason the surface has been rubbed down to the aluminum through the wash, which might happen if the wash has not been carefully applied, the whole surface must again be washed with'water, and the black spots that have come through must be scraped (not sanded), and more wash and tinning compound applied.

The mercury present in the cold tinning compound is very injurious to aluminum, and it is very important to keep the cold tinning compound away from the unprotected aluminum surface.

Itwill thus be observed that by means of an aluminum wash or a composition for the protection of the aluminum surface from the metallic mercury the same cold tinning compound which is applicable to steel and other ferrous metals may be used upon aluminum." This is a great advan-' Page, as it is necessary for the operator to buy only one type of tinning compound, and it is necessary for the inventor to stock only one type of tinning compound, which is of universal application. Needless to say, the tinning compound may also be used upon other metals, such as copper, iron, etc.

After the sprayed metal surface has been satisfactorily smoothed to the contour desired, the work piece, such asan automotive body, may then be refinished with paint in the usual manner, preferably by spraying.

The metal used for spraying is preferably the ordinary 30 to percent solder mixture, which may be purchased on the open market in various forms.

It will thus be observed that we have invented an improved tinning compound which is adapt'-' meltable solder composition,

2,149,826 compound may be used for tinning a surface to heat the surface to any substantial degree, but

warms it slightly, and the sprayed metal surface may be touched lightly with the hand immediately after spraying, in evidence of the fact that'it is not highly heated. Therefore, there is. no tendency for the plates which form the automotive vehicle body to buckle or warp due to excessive heat, nor is the which is applied to the inside of such steel bodies melted or damaged by the low degree of heat applied. Modern automotive bodiesnow have such a compound appliedto the interior of the body for the purpose of deadening sound, and the present spraying methods may be used without any damage to the sound deadening qualities of the lining on the metal body.

Perhaps one of the most important features of I the present method-and compositions is that the sprayed metal adheres so tightly to the prepared surfaces that there is no danger of the filling or coating ever coming off when subjected to the stress and strain and vibration which are incident to the use of the automotive vehicle.

While we have illustrateda preferred embodimentof our invention, many modifications may be made without departing from the spirit of the invention, and we do not wish to be limited to the precise details of construction set forth, but desire toavail ourselves of all changes within the scope of the appended claims.

Having thus described our invention, what we claim as new and desire to secure by Letters Patent of the United States, is: v I

1. The method of tinning aluminum for the application of a metal coating of solder which comprises grinding the aluminum surface to. provide a fresh metal contact surface, immediately applying a silver nitrate solution for the purpose of adding a coating of silver to the aluminum to, pro-' tect the aluminum from the action of mercury, applying copper sulphate in solution for the purpose of producing a layer of copper on the silver layer, and thereafter applying a tinning compound including bichloride of mercury and free mercury to form an amalgam, the copper and silvercoatings protecting the aluminum from the mercury.

2. The method of repairing aluminum bodies which comprises exposing a clean metal surface by abrasion of the aluminum body, applying an aluminum wash to said clean metal surface, said wash comprising of a solution of silver nitrate, applying a tinning sulphate, hydrochloric acid, bichloride of mercury, and an excess of metallic mercury, rubbing the cleaned metal surface with said compound until a uniform bright tinned surface'is produced, and applying metal to said surface in the form of a melted and reduced to a finely divided spray, and directed against the tinned surface by compressed air.

FRANK 0. ,ALBERTSOK. GUSTAV A. OLSEN.

tar or asphalt compound.

compound comprising copper 

